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Pyret: A new programming language from the creators of Racket

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Re: Pyret: A new programming language from the creators of Racket

#131

Post by f7t7ft7 »

geofft wrote: post #127
dagw wrote: post #105

Earlier quoted context omitted.

How many people taking intro to CS at MIT do you think are beginners who have never programmed before?

Quite a few, actually, which is why the Scheme class ended up being awful in practice -- you'd get a bimodal distribution of students where some are already familiar with multiple languages (usually more mainstream than Lisp) and some aren't familiar with any, and the class, by necessity, targeted the trough right between those. So it was too fast for the students who never programmed before, and either too slow or t…

I've seen an MIT Scheme class video, and it was painfully slow and the guy seemed to explain everything in painstaking detail. I've heard about the bimodal distribution, which I believe I witnessed among fellow students when I was taking classes. But I'm having trouble seeing how Scheme made it any worse or how the class was too fast.

And, Pyret looks like a terrible beginner language! I like PltScheme, but I can't see how anyone would ever want to use that.

Re: Pyret: A new programming language from the creators of Racket

#132

Post by skrishnamurthi »

geofft wrote: post #127
dagw wrote: post #105

Earlier quoted context omitted.

How many people taking intro to CS at MIT do you think are beginners who have never programmed before?

Quite a few, actually, which is why the Scheme class ended up being awful in practice -- you'd get a bimodal distribution of students where some are already familiar with multiple languages (usually more mainstream than Lisp) and some aren't familiar with any, and the class, by necessity, targeted the trough right between those. So it was too fast for the students who never programmed before, and either too slow or t…

The new course is so different in content from the old course that I don't think any pat comparison is meaningful.

At any rate, I went from being a staunch believer in the simplicity of Scheme's syntax to starting to think -- based on lots of observational data, and some preliminary studies (http://cs.brown.edu/~sk/Publications/Papers/Published/mfk-va...) -- that it's too simple (a failure of the "everything should be made as simple as possible, but not simpler" maxim).

But MIT's decisions are their own, and potentially peculiar to their specific curricular needs. Pyret was not influenced by them. Brown is proud to teach Racket and does so very successfully. Not every university is a dedicated follower of fashion!

Re: Pyret: A new programming language from the creators of Racket

#133

Post by skrishnamurthi »

dragonwriter wrote: post #83
gizmo wrote: post #7

Pyret looks like a there's a lot going on, based on the examples. It has implicit returns, special purpose syntax for data structures, iterators, assertions, refinements, etc. Having support for more stuff makes it less suitable as a teaching language, not more. Pyret looks like a has the good bits of Python plus a whole bunch of other cool stuff. But the language is pretty complex as a result. Cool? Yup! Good for te…

I don't see why a complex language can't be good for teaching if its designed in such a way that the complexity is optional, and you can use a focussed subset for pedagogical purposes (especially when the language supports using different focussed subsets depending on the specific focus of pedagogy.) I mean, even if you look at how language like Scheme/Racket, or Python, or pretty much any other language is used in t…

This is true of all educational settings -- except that the language subset then becomes an unenforced (and hence very leaky) abstraction. Students inadvertently step outside the subset and get either bizarre errors or, worse, their program runs and produces strange errors.

DrRacket pioneered the notion of "language levels" that grow with the student's needs. Pyret will end up taking some variant of this route. It's just too early to design those levels yet.

Re: Pyret: A new programming language from the creators of Racket

#134

Post by skrishnamurthi »

gizmo wrote: post #7

Pyret looks like a there's a lot going on, based on the examples. It has implicit returns, special purpose syntax for data structures, iterators, assertions, refinements, etc. Having support for more stuff makes it less suitable as a teaching language, not more. Pyret looks like a has the good bits of Python plus a whole bunch of other cool stuff. But the language is pretty complex as a result. Cool? Yup! Good for te…

DrRacket pioneered the notion of "language levels" that grow with the student's needs. Pyret will end up taking some variant of this route. It's just too early to design those levels yet. Once we have more experimental data about what kinds of inadvertent mistakes students make, we'll be in a position to say, "Oh, yeah, that was a bad thing to release on day 1", etc.

Re: Pyret: A new programming language from the creators of Racket

#135

Post by skrishnamurthi »

timtadh wrote: post #94
ek wrote: post #14

Earlier quoted context omitted.

I would encourage you to view the syntax as "Python, but repaired", for the following reasons: 1. Pyret comes out of Shriram's group's expertise with pinning down exactly what Python and other dynamic scripting languages do right, and (mostly) do wrong. Check out their recent paper Python: The Full Monty: A Tested Semantics for the Python Programming Language http://cs.brown.edu/~sk/Publications/Papers/Published/pmmw…

Thanks for the link to that paper. Super interesting to see actual semantics for python come out. It would be nice if this leads to better tooling for analysis of the language. Currently, it is pretty hard to bootstrap anything for the language in comparison with what you can do for the JVM.

You'd first have to fix Python's broken notion of scope. If you want to read only one, simple, page, read the last page (appendix 2 on variable renaming). Pyret was created to not have such problems by design.

Re: Pyret: A new programming language from the creators of Racket

#136

Post by acjohnson55 »

mercurial wrote: post #124
skrishnamurthi wrote: post #77

Earlier quoted context omitted.

It's actually widely used in Racket already. Yesterday a lead programmer at a major financial institution told me that he liked that style so much, he'd incorporated it into his company's OCaml system, and they use it in their production systems (lots of high-volume trading). Hardly "failure"s. Nevertheless, perhaps you could provide some pointers to the "many" projects that have tried it before? Assertions are not t…

This might work better for pure functions. I can't imagine it working very well for complex, stateful code which requires mocking and resetting the state between tests.

They didn't say one way or the other whether the language was pure FP, but I don't think any of the examples featured mutuality

Re: Pyret: A new programming language from the creators of Racket

#137

Post by skrishnamurthi »

clhodapp wrote: post #115
lysium wrote: post #104

Earlier quoted context omitted.

At the other end are definitions of which several fit on a single line: data Color = Red | Black

Lines really aren't much of a thing: they are a single keypress, which generates a newline character and some autogenerated indentation from your editor. There's no real difficulty in breaking things up across two lines versus typing any other extra character (this touches on another issue, which is that I am of the opinion that the concept of code brevity estimation by line count comparison is fundamentally flawed,…

From the very beginning we have debated whether or not to make the initial stick optional. We wanted at least a semester of code to review before we made a decision. I personally lean toward making it optional and just have to persuade the others (-:. With that, you would be able to write

data Color: Red | Black | Green;

We did also initially discuss using = instead of : in places where we were defining things (functions, data). That's still not completely out of the question. That would get you to

data Color = Red | Green | Black;

We need a closing delimiter to avoid creating huge ambiguities in the grammar.

Re: Pyret: A new programming language from the creators of Racket

#138

Post by skrishnamurthi »

klrr wrote: post #10

This project seems really promising, but I got one concern. Lisp's syntax have been one of its strength for beginners. Easy to learn, easy to solve common errors. I don't see the point of having Python-like syntax really, the user could learn other syntax after they've understood programming .

I've programmed in and taught Lisp syntax for 24 years, much of it exclusively in that syntax. I've also extensively researched errors in parenthetical languages.

The simplicity of parens is widely regarded as a strength, but I believe it is also a weakness. There is too much regularity in the syntax, resulting in numerous errors. Programmers, especially beginning programmers, need more "guideposts" in their programs. Additionally, parsers also benefit from this when producing errors.

Re: Pyret: A new programming language from the creators of Racket

#139

Post by rayiner »

jpolitz wrote: post #110
kazagistar wrote: post #108

Somehow, it looks a lot more like lua with a bunch of type-checks and tests added then like python. No named parameters, no generators, no comprehensions that I can see, no focus on iteration in general, no significant indentation, etc. Instead: "end" syntax, unified number type, all blocks produce new scopes (not just functions), local variables are explicit instead of default, etc.

That's a useful comparison, thanks. While we were certainly inspired by Pythonic syntax, we have ended up somewhere slightly different. The note about local variables is particularly important; we actively don't want Python's model of variables and scope.

Its shocking to me that so many languages designed after Scheme get variable scoping wrong.

Re: Pyret: A new programming language from the creators of Racket

#140

Post by skrishnamurthi »

sparkie wrote: post #49
andybak wrote: post #12

Earlier quoted context omitted.

My jaw dropped slightly to see someone suggest Lisp syntax would be a better starting place for beginners than Python's syntax. Is it just me or is that a fairly unorthodox point of view?

I'd say the real trouble is teaching any syntax at all to beginners, because their first language really taints them for life. Most people will think of successive languages in terms of their first, until they learn many and are able to think more generally. Lisp has the advantage that it really teaches the general semantics of programming languages, because it's syntax is just the syntax tree, and it basically only…

I've programmed in and taught Lisp syntax for 24 years, much of it exclusively in that syntax. I've also extensively researched errors in parenthetical languages.

The simplicity of parens is widely regarded as a strength, but I believe it is also a weakness. There is too much regularity in the syntax, resulting in numerous errors. Programmers, especially beginning programmers, need more "guideposts" in their programs. Additionally, parsers also benefit from this when producing errors.

The developers of Pyret are drenched in Lisp syntax; we know it profoundly well. Pyret is a conscious attempt to fix what we regard as flaws with that syntax.

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